package org.frameworkset.elasticsearch;

public class Preconditions {
	private Preconditions() {}

	/**
	 * Ensures the truth of an expression involving one or more parameters to the calling method.
	 *
	 * @param expression a boolean expression
	 * @throws IllegalArgumentException if {@code expression} is false
	 */
	public static void checkArgument(boolean expression) {
		if (!expression) {
			throw new IllegalArgumentException();
		}
	}

	/**
	 * Ensures the truth of an expression involving one or more parameters to the calling method.
	 *
	 * @param expression a boolean expression
	 * @param errorMessage the exception message to use if the check fails; will be converted to a
	 *     string using {@link String#valueOf(Object)}
	 * @throws IllegalArgumentException if {@code expression} is false
	 */
	public static void checkArgument(boolean expression,  Object errorMessage) {
		if (!expression) {
			throw new IllegalArgumentException(String.valueOf(errorMessage));
		}
	}

	/**
	 * Ensures the truth of an expression involving one or more parameters to the calling method.
	 *
	 * @param expression a boolean expression
	 * @param errorMessageTemplate a template for the exception message should the check fail. The
	 *     message is formed by replacing each {@code %s} placeholder in the template with an
	 *     argument. These are matched by position - the first {@code %s} gets {@code
	 *     errorMessageArgs[0]}, etc.  Unmatched arguments will be appended to the formatted message
	 *     in square braces. Unmatched placeholders will be left as-is.
	 * @param errorMessageArgs the arguments to be substituted into the message template. Arguments
	 *     are converted to strings using {@link String#valueOf(Object)}.
	 * @throws IllegalArgumentException if {@code expression} is false
	 * @throws NullPointerException if the check fails and either {@code errorMessageTemplate} or
	 *     {@code errorMessageArgs} is null (don't let this happen)
	 */
	public static void checkArgument(boolean expression,
									  String errorMessageTemplate,
									  Object... errorMessageArgs) {
		if (!expression) {
			throw new IllegalArgumentException(format(errorMessageTemplate, errorMessageArgs));
		}
	}

	/**
	 * Ensures the truth of an expression involving the state of the calling instance, but not
	 * involving any parameters to the calling method.
	 *
	 * @param expression a boolean expression
	 * @throws IllegalStateException if {@code expression} is false
	 */
	public static void checkState(boolean expression) {
		if (!expression) {
			throw new IllegalStateException();
		}
	}

	/**
	 * Ensures the truth of an expression involving the state of the calling instance, but not
	 * involving any parameters to the calling method.
	 *
	 * @param expression a boolean expression
	 * @param errorMessage the exception message to use if the check fails; will be converted to a
	 *     string using {@link String#valueOf(Object)}
	 * @throws IllegalStateException if {@code expression} is false
	 */
	public static void checkState(boolean expression,  Object errorMessage) {
		if (!expression) {
			throw new IllegalStateException(String.valueOf(errorMessage));
		}
	}

	/**
	 * Ensures the truth of an expression involving the state of the calling instance, but not
	 * involving any parameters to the calling method.
	 *
	 * @param expression a boolean expression
	 * @param errorMessageTemplate a template for the exception message should the check fail. The
	 *     message is formed by replacing each {@code %s} placeholder in the template with an
	 *     argument. These are matched by position - the first {@code %s} gets {@code
	 *     errorMessageArgs[0]}, etc.  Unmatched arguments will be appended to the formatted message
	 *     in square braces. Unmatched placeholders will be left as-is.
	 * @param errorMessageArgs the arguments to be substituted into the message template. Arguments
	 *     are converted to strings using {@link String#valueOf(Object)}.
	 * @throws IllegalStateException if {@code expression} is false
	 * @throws NullPointerException if the check fails and either {@code errorMessageTemplate} or
	 *     {@code errorMessageArgs} is null (don't let this happen)
	 */
	public static void checkState(boolean expression,
								   String errorMessageTemplate,
								   Object... errorMessageArgs) {
		if (!expression) {
			throw new IllegalStateException(format(errorMessageTemplate, errorMessageArgs));
		}
	}

	/**
	 * Ensures that an object reference passed as a parameter to the calling method is not null.
	 *
	 * @param reference an object reference
	 * @return the non-null reference that was validated
	 * @throws NullPointerException if {@code reference} is null
	 */
	public static <T> T checkNotNull(T reference) {
		if (reference == null) {
			throw new NullPointerException();
		}
		return reference;
	}

	/**
	 * Ensures that an object reference passed as a parameter to the calling method is not null.
	 *
	 * @param reference an object reference
	 * @param errorMessage the exception message to use if the check fails; will be converted to a
	 *     string using {@link String#valueOf(Object)}
	 * @return the non-null reference that was validated
	 * @throws NullPointerException if {@code reference} is null
	 */
	public static <T> T checkNotNull(T reference,  Object errorMessage) {
		if (reference == null) {
			throw new NullPointerException(String.valueOf(errorMessage));
		}
		return reference;
	}

	/**
	 * Ensures that an object reference passed as a parameter to the calling method is not null.
	 *
	 * @param reference an object reference
	 * @param errorMessageTemplate a template for the exception message should the check fail. The
	 *     message is formed by replacing each {@code %s} placeholder in the template with an
	 *     argument. These are matched by position - the first {@code %s} gets {@code
	 *     errorMessageArgs[0]}, etc.  Unmatched arguments will be appended to the formatted message
	 *     in square braces. Unmatched placeholders will be left as-is.
	 * @param errorMessageArgs the arguments to be substituted into the message template. Arguments
	 *     are converted to strings using {@link String#valueOf(Object)}.
	 * @return the non-null reference that was validated
	 * @throws NullPointerException if {@code reference} is null
	 */
	public static <T> T checkNotNull(T reference,
									  String errorMessageTemplate,
									  Object... errorMessageArgs) {
		if (reference == null) {
			// If either of these parameters is null, the right thing happens anyway
			throw new NullPointerException(format(errorMessageTemplate, errorMessageArgs));
		}
		return reference;
	}

  /*
   * All recent hotspots (as of 2009) *really* like to have the natural code
   *
   * if (guardExpression) {
   *    throw new BadException(messageExpression);
   * }
   *
   * refactored so that messageExpression is moved to a separate String-returning method.
   *
   * if (guardExpression) {
   *    throw new BadException(badMsg(...));
   * }
   *
   * The alternative natural refactorings into void or Exception-returning methods are much slower.
   * This is a big deal - we're talking factors of 2-8 in microbenchmarks, not just 10-20%.  (This
   * is a hotspot optimizer bug, which should be fixed, but that's a separate, big project).
   *
   * The coding pattern above is heavily used in java.util, e.g. in ArrayList.  There is a
   * RangeCheckMicroBenchmark in the JDK that was used to test this.
   *
   * But the methods in this class want to throw different exceptions, depending on the args, so it
   * appears that this pattern is not directly applicable.  But we can use the ridiculous, devious
   * trick of throwing an exception in the middle of the construction of another exception.  Hotspot
   * is fine with that.
   */

	/**
	 * Ensures that {@code index} specifies a valid <i>element</i> in an array, list or string of size
	 * {@code size}. An element index may range from zero, inclusive, to {@code size}, exclusive.
	 *
	 * @param index a user-supplied index identifying an element of an array, list or string
	 * @param size the size of that array, list or string
	 * @return the value of {@code index}
	 * @throws IndexOutOfBoundsException if {@code index} is negative or is not less than {@code size}
	 * @throws IllegalArgumentException if {@code size} is negative
	 */
	public static int checkElementIndex(int index, int size) {
		return checkElementIndex(index, size, "index");
	}

	/**
	 * Ensures that {@code index} specifies a valid <i>element</i> in an array, list or string of size
	 * {@code size}. An element index may range from zero, inclusive, to {@code size}, exclusive.
	 *
	 * @param index a user-supplied index identifying an element of an array, list or string
	 * @param size the size of that array, list or string
	 * @param desc the text to use to describe this index in an error message
	 * @return the value of {@code index}
	 * @throws IndexOutOfBoundsException if {@code index} is negative or is not less than {@code size}
	 * @throws IllegalArgumentException if {@code size} is negative
	 */
	public static int checkElementIndex(
			int index, int size,  String desc) {
		// Carefully optimized for execution by hotspot (explanatory comment above)
		if (index < 0 || index >= size) {
			throw new IndexOutOfBoundsException(badElementIndex(index, size, desc));
		}
		return index;
	}

	private static String badElementIndex(int index, int size, String desc) {
		if (index < 0) {
			return format("%s (%s) must not be negative", desc, index);
		} else if (size < 0) {
			throw new IllegalArgumentException("negative size: " + size);
		} else { // index >= size
			return format("%s (%s) must be less than size (%s)", desc, index, size);
		}
	}

	/**
	 * Ensures that {@code index} specifies a valid <i>position</i> in an array, list or string of
	 * size {@code size}. A position index may range from zero to {@code size}, inclusive.
	 *
	 * @param index a user-supplied index identifying a position in an array, list or string
	 * @param size the size of that array, list or string
	 * @return the value of {@code index}
	 * @throws IndexOutOfBoundsException if {@code index} is negative or is greater than {@code size}
	 * @throws IllegalArgumentException if {@code size} is negative
	 */
	public static int checkPositionIndex(int index, int size) {
		return checkPositionIndex(index, size, "index");
	}

	/**
	 * Ensures that {@code index} specifies a valid <i>position</i> in an array, list or string of
	 * size {@code size}. A position index may range from zero to {@code size}, inclusive.
	 *
	 * @param index a user-supplied index identifying a position in an array, list or string
	 * @param size the size of that array, list or string
	 * @param desc the text to use to describe this index in an error message
	 * @return the value of {@code index}
	 * @throws IndexOutOfBoundsException if {@code index} is negative or is greater than {@code size}
	 * @throws IllegalArgumentException if {@code size} is negative
	 */
	public static int checkPositionIndex(int index, int size,  String desc) {
		// Carefully optimized for execution by hotspot (explanatory comment above)
		if (index < 0 || index > size) {
			throw new IndexOutOfBoundsException(badPositionIndex(index, size, desc));
		}
		return index;
	}

	private static String badPositionIndex(int index, int size, String desc) {
		if (index < 0) {
			return format("%s (%s) must not be negative", desc, index);
		} else if (size < 0) {
			throw new IllegalArgumentException("negative size: " + size);
		} else { // index > size
			return format("%s (%s) must not be greater than size (%s)", desc, index, size);
		}
	}

	/**
	 * Ensures that {@code start} and {@code end} specify a valid <i>positions</i> in an array, list
	 * or string of size {@code size}, and are in order. A position index may range from zero to
	 * {@code size}, inclusive.
	 *
	 * @param start a user-supplied index identifying a starting position in an array, list or string
	 * @param end a user-supplied index identifying a ending position in an array, list or string
	 * @param size the size of that array, list or string
	 * @throws IndexOutOfBoundsException if either index is negative or is greater than {@code size},
	 *     or if {@code end} is less than {@code start}
	 * @throws IllegalArgumentException if {@code size} is negative
	 */
	public static void checkPositionIndexes(int start, int end, int size) {
		// Carefully optimized for execution by hotspot (explanatory comment above)
		if (start < 0 || end < start || end > size) {
			throw new IndexOutOfBoundsException(badPositionIndexes(start, end, size));
		}
	}

	private static String badPositionIndexes(int start, int end, int size) {
		if (start < 0 || start > size) {
			return badPositionIndex(start, size, "start index");
		}
		if (end < 0 || end > size) {
			return badPositionIndex(end, size, "end index");
		}
		// end < start
		return format("end index (%s) must not be less than start index (%s)", end, start);
	}

	/**
	 * Substitutes each {@code %s} in {@code template} with an argument. These are matched by
	 * position: the first {@code %s} gets {@code args[0]}, etc.  If there are more arguments than
	 * placeholders, the unmatched arguments will be appended to the end of the formatted message in
	 * square braces.
	 *
	 * @param template a non-null string containing 0 or more {@code %s} placeholders.
	 * @param args the arguments to be substituted into the message template. Arguments are converted
	 *     to strings using {@link String#valueOf(Object)}. Arguments can be null.
	 */
	// Note that this is somewhat-improperly used from Verify.java as well.
	static String format(String template,  Object... args) {
		template = String.valueOf(template); // null -> "null"

		// start substituting the arguments into the '%s' placeholders
		StringBuilder builder = new StringBuilder(template.length() + 16 * args.length);
		int templateStart = 0;
		int i = 0;
		while (i < args.length) {
			int placeholderStart = template.indexOf("%s", templateStart);
			if (placeholderStart == -1) {
				break;
			}
			builder.append(template.substring(templateStart, placeholderStart));
			builder.append(args[i++]);
			templateStart = placeholderStart + 2;
		}
		builder.append(template.substring(templateStart));

		// if we run out of placeholders, append the extra args in square braces
		if (i < args.length) {
			builder.append(" [");
			builder.append(args[i++]);
			while (i < args.length) {
				builder.append(", ");
				builder.append(args[i++]);
			}
			builder.append(']');
		}

		return builder.toString();
	}
}
